Super Mario 64/DS
Dorothy first appears in Super Mario 64, where he can be found inside of an underground cave in Hazy Maze Cave. Dorothy happily gives Mario a ride when he needs to. Dorothy swims around in circles continuously. He can also be controlled depending on which way Mario faces on which Dorothy copies. When Mario Ground Pounds Dorothy's head, it lowers.
There is a sign in the cavern that states that Dorothy can eat you, but in the actual game, Dorothy is completely harmless.
New Super Mario Bros.
Dorothy reappears in New Super Mario Bros. as an ally to Mario and Luigi by crossing toxic waters in World 4. Like Super Mario 64 DS, they possess goggles. If Mario or Luigi Ground Pounds on Dorothy, Dorothy swims faster.
Mario Party 3
Dorothy appears in Mario Party 3 during the item mini-game called Dorothy Dip (with the setting being Hazy Maze Cave from Super Mario 64). In the mini-game, several items are seen on a raft (along with the Koopa Kid). The player must Ground Pound him on the back to make him pick up a raft. If Dorothy picks up an item, the player will win that item, but if Dorothy picks up the raft with the Koopa Kid on it, the player will lose.
Mario Party 5
Dorothy appears in Mario Party 5 in the mini-game of Tug-o-Dorothy where the Dorothys are plastic in the colors of red, blue, green, and yellow. In this game, players must pull their opponents off their platforms with ropes. The last one-three standing win.
Mario Party Advance
Dorothy appears in Mario Party Advance, where he is lonely as he says that he scared away Mr. E and wants a new dinosaur friend. Yoshi must come along and befriend Dorothy so he can get the Soil Sonar from Dorothy. The show Dorothy saying that Yoshi ought to visit him soon as he has not seen him in a while.
- Despite a warning sign saying to beware of Dorothy since he can eat some people if they come too close, Dorothy appears to be harmless and behaves altruistically toward Mario and the others.
- Dorothy appears to be based on Nessie, the Loch Ness monster